Dilatation balloon catheters are frequently used for the treatment of stenoses in the coronary arteries. This procedure, known as percutaneous transluminal coronary angioplasty (PCTA), was developed by Dr. Andreas Gruntzig. According to this procedure, blockage in a coronary artery can be reduced by positioning a balloon dilatation catheter across the blockage and inflating the balloon, which causes stretching of the artery and pressing of the lesion into the artery wall to reestablish acceptable blood flow through the artery.
To move through the artery, the deflated balloon diameter should be as small as possible. The core or inner tube diameter of the catheter should be minimized along with the balloon, which can be done by folding, wrapping or twisting the balloon to achieve the smallest profile possible or by reducing wall thicknesses, to the extent possible, of the balloon itself. This deflated diameter affects the ease and ability of the dilatation catheter to pass through a guide catheter and through the coronary arteries leading to the stenosis to be opened.
In order to keep the outer diameter of the balloon catheter in its deflated condition, it is common to use a balloon protector. A balloon protector protects the balloon and distal tip of the catheter from possible damage during storage and keeps the balloon tightly wrapped in its deflated condition to minimize the outer diameter of the balloon in its deflated state. During the sterilization process, the catheter, with the balloon protector in place, is exposed to an elevated temperature for a period of time which causes the balloon to be heat set in the folded or wrapped configuration in which it is held by the balloon protector. This heat setting of a balloon gives the balloon a memory so that when it is inflated and deflated during an angioplasty procedure, the deflation will cause the balloon to return to its tightly wrapped heat set shape. This heat set shape will give the balloon a low profile diameter which will help when moving the catheter to a new stenosis or removal of the catheter after the procedure has been performed.
Various types and configurations of balloon protectors have been shown in the prior art, for example, in U.S. Pat. Nos. 4,738,666 and 4,710,181 to Fuqua, in U.S. Pat. No. 5,053,007 to Euteneuer, U.S. Pat. No. 5,066,298 to Hess, U.S. Pat. No. 4,573,981 to McFarlane, U.S. Pat. No. 5,015,231 to Keith et al. and U.S. Pat. No. 5,137,512 to Burns et al.
The above-noted Fuqua '666 and '181 patents propose a catheter protector comprising a hollow cylindrical sheath. The Fuqua sheath covers the entire length of the catheter, and is removed by pulling it off of the proximal end of the catheter. Fuqua also proposes providing perforations in the sheath for facilitating its removal. The above-noted Euteneuer '007 patent proposes a compression protector employing an inner sleeve applied over a deflated- balloon, an outer sleeve applied over the inner sleeve, and a compression housing for compressing the outer sleeve radially on the inner sleeve, thus compressing the inner sleeve radially on the balloon. The above-noted Hess '298 patent proposes protecting a catheter's balloon by wrapping the balloon with tape in an overlapping fashion. The above-noted McFarlane '981 patent proposes a substantially tapered cylindrical sheath which encloses a distal portion of the catheter assembly and is locked in place with two finger elements. The above noted Keith '231 patent proposes a multipart balloon protector consisting of an inner sleeve, with an elongated expansion slit to facilitate installation over the balloon, and a second outer sleeve compressing the inner sleeve. The above noted Burns '512 patent proposes a multisegment balloon protector using two protectors that cover different areas of the balloon.